You don't say how much you was consuming. Green tea does, as Steve says, contain caffeine. 400mg a day is the upper recommended daily dose. 1000mg can and has caused medical issues of the type you describe.
In one well publicized (here) example a well-known online supplement company had their name in the national press after a young idiot took a teaspoonful of caffeine at a party while drunk. That's 5000mg!! He was very lucky. Probably, cos he was young.